In general, for use e.g. in controlling the behavior of a vehicle, respective rotational speeds of a plurality of wheels are calculated. More specifically, the angular speed of each wheel is detected by a sensor, and the wheel speed of each wheel is calculated based on the detected angular speed and a predetermined diameter of the wheel. However, the above-described method cannot accurately calculate the wheel speed when the actual diameter of the wheel is changed from the predetermined diameter due to aging thereof or there is a variation in the actual diameter between individual wheels. To solve this problem, conventionally, the diameters of the wheels are corrected. This method is disclosed e.g. in Patent Literature 1, in which, similarly to the above, the wheel speeds of the plurality of wheels are calculated, respectively, and an average value of the calculated wheel speeds of the respective wheels is calculated, whereafter based on the difference between the average value and the calculated wheel speeds of the respective wheels, the diameters of the wheels are corrected.
As described above, in the conventional method, the difference between the average value of the wheel speeds of the respective wheels and the calculated wheel speed of each wheel is used as a parameter indicative of a change in diameter of the wheel. However, the average value of the wheel speeds of the wheels is obtained by generally averaging all the wheel speeds, and hence the difference between the average value thus obtained and the calculated wheel speed of each wheel cannot directly represent relative variation in diameter between wheels, which makes it impossible to properly detect the relative variation in diameter between the wheels.
The present invention has been made to provide a solution to the above-described problems, and an object thereof is to provide a wheel diameter variation-detecting device which is capable of properly detecting relative variation in diameter between a plurality of wheels of a vehicle.
[Patent Literature 1]
Japanese Laid-Open Patent Publication (Kokai) No. H04-283665